Compact zoom lens

ABSTRACT

A three-lens group zoom lens in an N-P-P configuration; the first, second, and third lens groups are arranged sequentially from an object side to an image side; during zooming from a wide-angle to a telephoto position the distance between the first lens group and the second lens group is reduced and the distance between the second lens group and the third lens group is changed, and the zoom lens satisfies the following inequalities 
       −1.3&lt; f   1   /f   2 &lt;−1.0 
       1.6&lt; f   2   /f   w &lt;2.3 
       4.5&lt; f   3   /f   w &lt;5.2,         where, f 1 , f 2 , and f 3 , respectively, denote the focal lengths of the first, second and third lens groups, and f w  denotes the focal length of the overall zoom lens at the wide-angle position.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2008-0077061, filed on Aug. 6, 2008, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens having a small and compactsize, wide viewing angle, and high magnification, and is thereby beingsuitable for use in various types of cameras.

2. Description of the Related Art

Recently, optical imaging apparatuses such as digital cameras or digitalcamcorders that use an image sensing device such as a charge coupleddevice (CCD) or a complementary metal-oxide semiconductor (CMOS) arewidely used. In addition, since the demand for high functional opticalimaging apparatuses having high magnification and wide viewing angle,low manufacturing costs, and small and lightweight structures hasincreased, the demand has similarly increased for zoom lenses for use insuch optical focusing apparatuses which have high performance, lowmanufacturing cost, and lightweight structures.

In general, a three-group zoom lens has an appropriate zooming functionand a relatively small size, and thus it can be easily used in compactand stylish digital cameras.

While three-group zoom lenses of various designs have been suggested, itis difficult to realize aberration correction and small zoom opticssimultaneously. For example, if the focal length of the first lens groupis set to be short in order to reduce the size of the zoom lens, thethickness of the zoom lens increases in order to correct the aberration,and thus, the overall length of the zoom lens also increases when thezoom lens is in standby status. In addition, when the first lens grouphas many aspherical surfaces, it becomes expensive to fabricate.

SUMMARY OF THE INVENTION

The present invention provides a zoom lens having small size, wideviewing angle, and high magnification.

According to an aspect of the present invention, there is provided azoom lens including: a first lens group having a negative refractivepower; a second lens group having a positive refractive power; and athird lens group having a positive refractive power, wherein the first,second, and third lens groups may be arranged sequentially from anobject side to an image side, and the lens groups are moved duringzooming from a wide-angle position to a telephoto position so that thedistance between the first lens group and the second lens group can bereduced and the distance between the second lens group and the thirdlens group can be changed, and the zoom lens satisfies the followinginequalities

−1.3<f ₁ /f ₂<−1.0

1.6<f ₂ /f _(w)<2.3

4.5<f ₃ /f _(w)<5.2,

where, f₁, f₂, f₃ and f_(w) respectively denote the focal length of thefirst lens group, the focal length of the second lens group, the focallength of the third lens group, and the overall focal length of the zoomlens at the wide-angle position.

The first lens group may include a meniscus lens that is convex towardthe object side and has a negative refractive power, and another lenshaving a positive refractive power. The zoom lens may satisfy thefollowing inequality

−2.2<f ₁₂ /f ₁₁×tan(ω w)<−1.9,

where f₁₁, f₁₂, and ω w respectively denote the focal length of thenegative lens in the first lens group, the focal length of the positivelens in the first lens group, and the half angle of view in thewide-angle position.

Both surfaces of the meniscus lens having a negative refractive powermay be aspherical surfaces. The third lens group may include onepositive lens, and the positive lens may include at least one asphericalsurface.

The second lens group may include four lenses that are arrangedsequentially from the object side to have positive refractive power,positive refractive power, negative refractive power, and positiverefractive power, respectively. A first lens facing the object in thesecond lens group may have at least one aspherical surface.

The zoom lens may satisfy the following inequality

1.0<L _(t) /L _(w)<1.2,

where L_(t) and L_(w) respectively denote the overall length of the zoomlens at the telephoto position and the wide-angle position.

According to another aspect of the present invention, there is provideda photographing apparatus including: a zoom lens according to anembodiment of the present invention; and a charge coupled devicereceiving an image formed by the zoom lens.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a diagram showing optical arrangements of a zoom lens atwide-angle position, middle-angle position, and telephoto positionaccording to an embodiment of the present invention;

FIG. 2 shows diagrams of spherical aberration, field curvature, anddistortion of the zoom lens at wide-angle position, middle-angleposition and telephoto position according to the embodiment of thepresent invention;

FIG. 3 is a diagram showing optical arrangements of a zoom lens atwide-angle position, middle-angle position and telephoto positionaccording to another embodiment of the present invention;

FIG. 4 shows diagrams of spherical aberration, field curvature, anddistortion of the zoom lens at wide-angle position, middle-angleposition and telephoto position according to another embodiment of thepresent invention;

FIG. 5 is a diagram showing optical arrangements of a zoom lens atwide-angle position, middle-angle position and telephoto positionaccording to another embodiment of the present invention; and

FIG. 6 shows diagrams of spherical aberration, field curvature, anddistortion of the zoom lens at wide-angle position, middle-angleposition and telephoto position according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. In the drawings, the thicknesses of layers andregions are exaggerated for clarity.

FIGS. 1, 3, and 5 are diagrams showing optical arrangements of a zoomlens at wide-angle, middle-angle and telephoto positions according tovarious embodiments of the present invention. Referring to FIGS. 1, 3and 5, the zoom lens includes a first lens group G1 having a negativerefractive power, a second lens group G2 having a positive refractivepower, and a third lens group G3 having a positive refractive power,which are arranged sequentially from an object O side to an image Iside. When zooming from wide-angle to telephoto positions, the firstlens group G1 moves along a path convex toward the image I side, thesecond lens group G2 moves monotonously toward the object O, and thethird lens group G3 moves such that the distance between the third lensgroup G3 and the second lens group G2 changes. That is, the lens groupsmove along an optical axis so that the distance between the first lensgroup G1 and the second lens group G2 is reduced and the distancebetween the second lens group G2 and the third lens group G3 is changed.

The zoom lens according to the present embodiment is configured so as tosatisfy the following inequality.

−1.3<f ₁ /f ₂<−1.0   (1)

where f₁, f₂ respectively denote focal lengths of the first lens groupG1 and the second lens group G2.

The above formula defines the ratio between the focal lengths of thefirst lens group G1 and the second lens group G2. When the ratio f₁/f₂increases beyond the maximum limit, the focal length of the first lensgroup G1 is reduced, and thus, it is difficult to compensate theaberration, and in particular, the distortion, at various zoompositions. When the ratio f₁/f₂ decreases below the minimum limit, themovement of the first lens group G1 increases during zooming, and thus,the overall length of the zoom lens increases.

In addition, the zoom lens according to the embodiments of the presentinvention may satisfy the following inequality.

1.6<f ₂ /f _(w)<2.3   (2)

where f₂ and f_(w) respectively denote the focal length of the secondlens group G2 and a focal length of the entire optics in the wide-angleposition.

The above formula defines the ratio between the focal length of thesecond lens group G2 and the focal length of the overall zoom lens atthe wide-angle position. When the ratio f₂/f_(w) increases beyond themaximum limit, the moving distance of the second lens group G2 increasesduring zooming, and thus, the overall length of the zoom lens increases.In addition, when the ratio f₂/f_(w) decreases below the minimum limit,the focal length of the second lens group G2 is reduced even though theoverall length of the zoom lens is increases, and thus, it is difficultto compensate the aberration throughout the zooming range.

In addition, the zoom lens according to the embodiments of the presentinvention may satisfy the following inequality.

4.5<f ₃ /f _(w)<5.2   (3)

where f₃ and f_(w) respectively denote the focal length of the thirdlens group G3 and the focal length of the overall zoom lens at thewide-angle position.

The above inequality defines a ratio between the focal length of thethird lens group G3 and the focal length of the overall zoom lens at thewide-angle position. When the ratio f₃/f_(w) increases beyond themaximum limit, an exit pupil becomes close to the image surface, andthus a telecentric property degrades. In addition, when the ratiof₃/f_(w) decreases below the minimum limit, the refractive power of thethird lens group G3 becomes stronger, and thus, astigmatism increasesalthough the telecentric property improves.

In addition, the zoom lens according to the embodiments of the presentinvention may satisfy the following inequality.

−2.2<f ₁₂ /f ₁₁×tan(ω w)<−1.9   (4)

where f₁₁, f₁₂, and ω w respectively denote the focal length of anegative lens in the first lens group G1, the focal length of a positivelens in the first lens group G1, and the half angle of view at thewide-angle position.

When the value f₁₂/f₁₁×tan(ω w) increases beyond the maximum limit, itis difficult to obtain a focal length suitable at the wide angleposition. In addition, when the value f₁₂/f₁₁×tan(ω w) decreases belowthe minimum limit, the refractive power of the negative lens in thefirst lens group G1 becomes stronger, and it is difficult to compensatethe aberration, in particular, the distortion, throughout the entirezoom range.

In addition, the zoom lens according to embodiments of the presentinvention may satisfy the following inequality.

1.0<L _(t) /L _(w)<1.2   (5)

where L_(t) and L_(w) respectively denote the overall length of the zoomlens at the telephoto position and the overall length of the zoom lensat the wide-angle position.

When the ratio L_(t)/L_(w) increases beyond the maximum limit, theoverall length of the zoom lens at the telephoto position becomesrelatively longer than that at the wide-angle position, and thus, themoving distance of the first lens group G1 and the second lens group G2increase. As a result, the zoom lens must is enlarged in order to ensurethe moving amount, and F number at the telephoto position increases. Inaddition, when the ratio L_(t)/L_(w) decreases below the minimum limit,the aperture of the lens in the first lens group G1 increases, and thus,it is difficult to reduce the size of the zoom lens.

Configurations and operations of the zoom lens will be described asfollows with reference to FIG. 1.

The first lens group G1 focuses a virtual image of an object, and movesnon-linearly during zooming in order to compensate for the change in thefocusing position of the overall zoom lens. The first lens group G1 mayinclude a first lens 110-1 that is a negative meniscus lens formed to beconvex toward the object side O, and a second lens 120-1 that is convextoward the object side O and has a positive refractive power. When thefirst lens group G1 is formed to include two lenses, the entirethickness of the first lens group G1 can be reduced and it is easy toassemble and adjust the lenses, and accordingly, the first lens group G1can be fabricated at relatively low cost. In addition, when the lensesfor the first lens group G1 having negative refractive power andpositive refractive power are sequentially arranged from the object sideO, coma aberration and distortion at the wide-angle position andspherical aberration at the telephoto position can be compensated for.In addition, both surfaces of the first lens 110-1, which is thenegative meniscus lens, may be aspherical surfaces. Accordingly, thedistortion at the wide-angle position can be compensated for, and theoverall refractive power of the first lens group G1 becomes stronger,thus, providing a compact zoom lens.

The second lens group G2 moves monotonously to perform zooming of thevirtual image generated by the first lens group G1. In general, thesecond lens group G2 in the three-group type zoom lens is a triplet lensincluding three lenses having positive, negative, and positiverefractive power, respectively. However, the second lens group G2 of thepresent embodiment includes four lenses. The second lens group G2 mayinclude, for example, a third lens 210-1 that is a positive lens, adoublet lens consisting of a fourth lens 220-1 that is a positive lensand a fifth lens 230-1 that is a negative lens, and a sixth lens 240-1that is a positive lens. The second lens group G2 of the presentembodiment has the above structure to address the following describeddisadvantages of the general triplet lens configuration.

When the second lens group is fabricated as a triplet structure and isdisposed behind the first lens group which has negative refractivepower, divergent light rays emitted from the first lens group areincident onto the second lens group, and thus, it is difficult tocompensate for the spherical aberration. In addition, in order toimprove compensation for negative distortion generated in the first lensgroup G1, the entire second lens group G2 should be arranged to have therefractive power of the telephoto type. In that case, strong refractivepower is concentrated on the positive lens located on the outermostportion of the second lens group G2, which faces the object side, andthus, it is difficult to compensate for the spherical aberration. Inorder to compensate for the spherical aberration using the second lensgroup of the triplet structure, the entire refractive power of thesecond lens group is substantially weakened, and thus, the size of thezoom lens increases. Therefore, it is difficult to achieve both acompact size of zoom lens and high performance of the zoom lens when thesecond lens group has the triplet structure.

Therefore, the zoom lens according to the present embodiment includesthe second lens group G2 that includes the third lens 210-1 that is apositive lens, the doublet lens consisting of the fourth lens 220-1 thatis a positive lens and the fifth lens 230-1 that is a negative lens, andthe sixth lens 240-1 that is a positive lens, which are arrangedsequentially from the object side along the optical axis. As a result,compensating for the distortion or chromatic aberration of magnificationis improved, and at the same time, the refractive power of the entiresecond lens group G2 can be strengthened and a more compact zoom lenscan be fabricated.

In addition, at least one surface of the third lens 210-1, which is thefirst lens of the second lens group G2 from the object side, may be anaspherical surface. Then, the spherical aberration and the comaaberration generated in the second lens group G2 can be improved well,and the refractive power of the second lens group G2 can be increased.In addition, in order to ensure the above effects, a surface of thethird lens 210-1 facing the object O may be an aspherical surface.

The third lens group G3 moves during zooming so that the exit pupil ofthe zoom lens can be located at a position where the light can beefficiently incident onto an imaging device, and at the same time,compensates for the aberration that cannot be compensated for by thefirst and second lens groups G1 and G2. The third lens group G3 mayinclude a seventh lens 310-1 that is a positive lens. Since the thirdlens group G3 consists of one lens, the entire thickness of the thirdlens group G3 is relatively small, and it is easy and economical toassemble the third lens group. In addition, at least one surface of theseventh lens 310-1 may be an aspherical surface, and accordingly, theastigmatism that is not compensated for by the first and second lensgroups G1 and G2 can be compensated for.

As described above, the zoom lens according to the embodiments of thepresent invention may satisfy the conditions given by inequalities 1 to5. Inequalities 1 to 5 can be modified in inequalities 6 to 10 forperforming the aberration compensation and for efficiently fabricating arelatively small zoom lens.

−1.2<f ₁ /f ₂<−1.1   (6)

1.8<f ₂ /f _(w)<2.1   (7)

4.7<f ₃ /f _(w)<5.0   (8)

−2.1<f ₁₂ /f ₁₁×tan(ω w)<−2.05   (9)

1.0<L _(t) /L _(w)<1.1   (10)

Hereinafter, detailed lens data according to embodiments of the presentinvention will be described as follows. The aspherical surface can bedefined as follows.

$\begin{matrix}{x = {\frac{c^{r}y^{2}}{1 + \sqrt{1 - {\left( {K + 1} \right)c^{\prime 2}y^{2}}}} + {Ay}^{4} + {By}^{6} + {Cy}^{8} + {Dy}^{10}}} & (11)\end{matrix}$

Here, x denotes the distance from the vertex of a lens on the opticalaxis direction, and y denotes the distance in a direction perpendicularto the optical axis direction. K denotes a conic constant and A, B, C,and D denote aspheric coefficients, and c′ denotes a reciprocal of theradius of curvature, 1/R, at the vertex of the lens.

Hereinafter, f denotes the focal length of the overall zoom lens, FNodenotes the F number, 2ω denotes the angle of view, L denotes theoverall length of the zoom lens, and ST denotes an aperture stop. Ri andDi respectively denote the radius of curvature of a surface i and adistance between the surface i and a surface (i+1). In addition, ni andvi respectively denote the refractive index of i-th member from theobject side O based on a d-line, and Abbe's number. In each of theembodiments, a variable distance between the lenses is D4, D12, or D14.Reference numerals of components are attached with the numbersindicating the first to third embodiments.

First Embodiment

FIG. 1 shows a zoom lens according to an embodiment of the presentinvention. The first lens group G1 includes the first lens 110-1 and thesecond lens 120-1, the second lens group G2 includes the third, fourth,fifth, and sixth lenses 210-1, 220-1, 230-1, and 240-1, and the thirdlens group G3 includes the seventh lens 310-1. In addition, P1 and P2denote an infrared ray filter and a cover glass.

R1 = 22.351 D1 = 1.10 N1 = 1.85800 v1 = 40.1 R2 = 4.227 D2 = 2.06 R3 =8.491 D3 = 1.65 N2 = 1.92286 v2 = 20.9 R4 = 17.696 D4 = variable R5 = STD5 = 0.00 R6 = 5.464 D6 = 1.39 N3 = 1.76600 v3 = 46.8 R7 = 48.725 D7 =0.34 R8 = 6.197 D8 = 1.18 N4 = 1.51742 v4 = 52.2 R9 = 31.379 D9 = 0.45N5 = 1.92286 v5 = 20.9 R10 = 4.018 D10 = 0.51 R11 = 38.236 D11 = 1.13 N6= 1.80518 v6 = 25.5 R12 = −15.812 D12 = variable R13 = 28.620 D13 = 1.54N7 = 1.51470 v7 = 63.8 R14 = −21.925 D14 = variable R15 = ∞ D15 = 0.30N8 = 1.51678 v8 = 64.2 R16 = ∞ D16 = 0.30 R17 = ∞ D17 = 0.50 N9 =1.51678 v9 = 64.2 R18 = ∞

Deformation term R1 surface K = 0.00000E+00 A = −6.65409E−04 B =2.19545E−05 C = −3.66287E−07 D = 2.36025E−09 R2 surface K = −4.63912E−01A = −1.06486E−03 B = −1.36362E−05 C = 1.46498E−06 D = −5.67865E−08 R6surface K = −1.00000E+00 A = 3.48355E−04 B = 0.00000E+00 C = 0.00000E+00D = 0.00000E+00 R14 surface K = −3.53781E−01 A = 7.32041E−05 B =1.44298E−05 C = −1.14533E−06 D = 2.56088E−08

wide middle telephoto F 5.09 10.00 19.21 F no 2.84 4.00 6.04 2ω 77.643.0 22.9 L 34.87 31.64 36.87

Variable distance D4 14.24 5.69 1.00 D12 4.67 10.73 20.21 D14 3.14 2.402.80

FIG. 2 shows diagrams of longitudinal spherical aberration, anastigmatic field curvature, and distortion of the zoom lens according tothe current embodiment of the present invention at (a) wide-angleposition, (b) middle-angle position, and (c) telephoto position,respectively. The longitudinal spherical aberrations are with respect toa line c having a wavelength of 656.28 nm, a line d having a wavelengthof 587.56 nm, and a line f having a wavelength of 486.13 nm. The fieldcurvature includes a tangential field curvature (T) and a sagittal fieldcurvature (S), which are respectively represented by a dotted line and asolid line.

Second Embodiment

FIG. 3 shows a zoom lens according to another embodiment of the presentinvention. The first lens group G1 includes the first and second lenses110-2 and 120-2, the second lens group G2 includes the third, fourth,fifth, and sixth lenses 210-2, 220-2, 230-2, and 240-2, and the thirdlens group G3 includes the seventh lens 310-2. In addition, P1 and P2denote an infrared ray filter and a cover glass.

R1 = 24.088 D1 = 1.10 N1 = 1.85800 v1 = 40.1 R2 = 4.286 D2 = 2.03 R3 =8.416 D3 = 1.67 N2 = 1.92286 v2 = 20.9 R4 = 17.647 D4 = variable R5 = STD5 = 0.00 R6 = 5.566 D6 = 1.38 N3 = 1.76600 v3 = 46.8 R7 = 58.838 D7 =0.35 R8 = 6.236 D8 = 1.19 N4 = 1.51742 v4 = 52.2 R9 = 34.448 D9 = 0.45N5 = 1.92286 v5 = 20.9 R10 = 4.092 D10 = 0.52 R11 = 71.173 D11 = 1.12 N6= 1.80518 v6 = 25.5 R12 = −13.958 D12 = variable R13 = 18.321 D13 = 1.57N7 = 1.51678 v7 = 64.2 R14 = −43.056 D14 = variable R15 = ∞ D15 = 0.30N8 = 1.51678 v8 = 64.2 R16 = ∞ D16 = 0.30 R17 = ∞ D17 = 0.50 N9 =1.51678 v9 = 64.2 R18 = ∞

Aspheric coefficients R1 surface K = 0.00000E+00 A = −4.66680E−04 B =1.41568E−05 C = −2.15957E−07 D = 1.34781E−09 R2 surface K = −4.62184E−01A = −7.88756E−04 B = −1.55754E−05 C = 1.12464E−06 D = −4.19529E−08 R6surface K = −1.00000E+00 A = 3.04490E−04 B = 0.00000E+00 C = 0.00000E+00D = 0.00000E+00

Wide middle telephoto f 5.04 10.00 19.26 F no 2.82 3.98 6.03 2ω 78.443.3 23.0 L 35.06 31.73 37.06

Variable distances D4 14.48 5.67 0.98 D12 4.52 10.70 20.42 D14 3.22 2.512.81

FIG. 4 shows diagrams of longitudinal spherical aberration, astigmaticfield curvature, and distortion of the zoom lens according to thecurrent embodiment of the present invention at (a) wide-angle position,(b) middle-angle position, and (c) telephoto positions, respectively.The longitudinal spherical aberrations are with respect to a line chaving a wavelength of 656.28 nm, a line d having a wavelength of 587.56nm, and a line f having a wavelength of 486.13 nm. The field curvatureincludes a tangential field curvature (T) and a sagittal field curvature(S), which are respectively represented by a dotted line and a solidline.

Third Embodiment

FIG. 5 shows a zoom lens according to another embodiment of the presentinvention. The first lens group G1 includes the first and second lenses110-3 and 120-3, the second lens group G2 includes the third, fourth,fifth, and sixth lenses 210-3, 220-3, 230-3, and 240-3, and the thirdlens group G3 includes the seventh lens 310-3. In addition, P1 and P2denote an infrared ray filter and a cover glass.

R1 = 21.4172 D1 = 1.1 N1 = 1.85800 v1 = 40.1 R2 = 4.14907 D2 = 2.02568R3 = 8.20443 D3 = 1.64259 N2 = 1.92286 v2 = 20.9 R4 = 15.99 D4 =variable R5 = ST D5 = 0.00 R6 = 5.2306 D6 = 1.53654 N3 = 1.76600 v3 =46.8 R7 = −163.89 D7 = 0.25622 R8 = 7.16589 D8 = 1.19205 N4 = 1.51742 v4= 52.2 R9 = 220.228 D9 = 0.45 N5 = 1.92286 v5 = 20.9 R10 = 3.8578 D10 =0.56808 R11 = 18.4079 D11 = 0.9971 N6 = 1.92286 v6 = 20.9 R12 = −35.873D12 = variable R13 = 16.2882 D13 = 1.62219 N7 = 1.48745 v7 = 70.4 R14 =−40.957 D14 = variable R15 = ∞ D15 = 0.30 N8 = 1.51678 v8 = 64.2 R16 = ∞D16 = 0.30 R17 = ∞ D17 = 0.50 N9 = 1.51678 v9 = 64.2 R18 = ∞

Aspheric coefficients R1 surface K = 0.00000E+00 A = −4.66680E−04 B =1.41568E−05 C = −2.15957E−07 D = 1.34781E−09 R2 surface K = −4.62184E−01A = −7.88756E−04 B = −1.55754E−05 C = 1.12464E−06 D = −4.19529E−08 R6surface K = −1.00000E+00 A = 3.04490E−04 B = 0.00000E+00 C = 0.00000E+00D = 0.00000E+00

Wide middle telephoto f 5.04 9.58 18.30 F no 2.83 3.81 5.88 2ω 75.9 44.624.2 L 33.00 29.44 34.86

Variable distances D4 13.20 4.91 1.00 D12 4.62 8.52 18.20 D14 2.32 3.152.80

FIG. 6 shows diagrams of longitudinal spherical aberration, astigmaticfield curvature, and distortion of the zoom lens according to thecurrent embodiment of the present invention at (a) wide-angle position,(b) middle-angle position, and (c) telephoto positions, respectively.The longitudinal spherical aberrations are with respect to a line chaving a wavelength of 656.28 nm, a line d having a wavelength of 587.56nm, and a line f having a wavelength of 486.13 nm. The field curvatureincludes a tangential field curvature (T) and a sagittal field curvature(S), which are respectively represented by a dotted line and a solidline.

The following table shows that the zoom lenses according to the aboveembodiments satisfy inequalities 1 to 5.

Embodiment 1 Embodiment 2 Embodiment 3 Inequality 1 −1.149 −1.147 −1.173Inequality 2 1.968 2.007 1.857 Inequality 3 4.768 4.959 4.775 Inequality4 −2.094 −2.100 −2.081 Inequality 5 1.056 1.057 1.056

According to the zoom lens of the embodiments of the present invention,a peripheral illuminance in the entire variation region can besufficiently ensured, the field curvature can be compensated forefficiently, and the length of the zoom lens can be reduced when thezoom lens is retracted. Accordingly, the compact zoom lens can befabricated more economically. The above zoom lens can be used inphotographing apparatuses such as digital cameras, and thus, an opticalapparatus having a small size and high optical performance can berealized.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A zoom lens comprising: a first lens group having a negativerefractive power; a second lens group having a positive refractivepower; and a third lens group having a positive refractive power,wherein the first, second, and third lens groups are arrangedsequentially from an object side to an image side, and the lens groupsare moved during zooming from a wide-angle position to a telephotoposition so that the distance between the first lens group and thesecond lens group is reduced and the distance between the second lensgroup and the third lens group is changed, and the zoom lens satisfiesthe following inequalities−1.3<f ₁ /f ₂<−1.01.6<f ₂ /f _(w)<2.34.5<f ₃ /f _(w)<5.2, where, f₁, f₂, f₃ and f_(w) respectively denote thefocal length of the first lens group, the focal length of the secondlens group, the focal length of the third lens group, and the overallfocal length of the zoom lens at the wide-angle position.
 2. The zoomlens of claim 1, wherein the first lens group includes a meniscus lensthat is convex toward the object side and has a negative refractivepower, and another lens having a positive refractive power.
 3. The zoomlens of claim 2, wherein the zoom lens satisfies the followinginequality−2.2<f ₁₂ /f ₁₁×tan(ω w)<−1.9, where f₁₁, f₁₂, and ω w respectivelydenote the focal length of the negative lens in the first lens group,the focal length of the positive lens in the first lens group, and ahalf angle of view at the wide-angle position.
 4. The zoom lens of claim2, wherein both surfaces of the meniscus lens having a negativerefractive power are aspherical surfaces.
 5. The zoom lens of claim 1,wherein the third lens group includes one positive lens.
 6. The zoomlens of claim 5, wherein the positive lens in the third lens groupincludes at least one aspherical surface.
 7. The zoom lens of claim 1,wherein the second lens group includes four lenses that are arrangedsequentially from the object side to have positive refractive power,positive refractive power, negative refractive power, and positiverefractive power, respectively.
 8. The zoom lens of claim 7, wherein thefirst lens closest to the object side in the second lens group has atleast one aspherical surface.
 9. The zoom lens of claim 1, wherein thezoom lens satisfies the following inequality1.0<L _(t) /L _(w)<1.2, where L_(t) and L_(w) respectively denotelengths of the overall zoom lens at the telephoto position and thewide-angle position.
 10. A photographing apparatus comprising: a zoomlens according to claim 1; and a charge coupled device receiving animage formed by the zoom lens.